SE542648C2

SE542648C2 - Integrated residual current device for handheld wet tools

Info

Publication number: SE542648C2
Application number: SE1651345A
Authority: SE
Inventors: Rosén Magnus; Linnér Johan; Berg Johan
Original assignee: Husqvarna Ab
Priority date: 2016-10-13
Filing date: 2016-10-13
Publication date: 2020-06-23
Also published as: SE1651345A1; EP3526870B1; US10666041B2; EP3526870A4; WO2018070929A1; AU2017342682B2; EP3526870A1; US20190348831A1; AU2017342682A1

Abstract

Disclosed herein is an integrated residual current device (102), RCD, for a liquid system tool. The liquid system tool comprises a current circuit having a power input (101, 210) for receiving an alternating electrical current, AC, a rectifier (104, 204, 402) for rectifying the AC into a direct current, DC, a voltage booster (106, 220) for increasing a DC voltage and a motor unit (111, 230) connected to an output of the voltage booster (106, 220) for driving the liquid system tool.The RCD comprises a sensor element (105, 205, 302, 403a-e) connected to an output of the rectifier (104, 204, 402) and an input of the voltage booster (106, 220) and being configured to collect an analog current signal and an analog to digital, A/D, converter (109, 209, 303, 403a, 403b) configured to convert the analog current signal into a digital current signal. The integrated RCD (102) further comprises a logic unit (108, 208, 304, 405) connected to the A/D converter (109, 209, 303, 403a, 403b), wherein the logic unit (108, 208, 304, 405) is configured to evaluate the digital current signal and compare it to a current requirement, and wherein if the logic unit (108, 208, 304, 405) determines that the digital current signal does not fulfill the current requirement, it is further configured to break the current circuit so that no current can flow in the liquid system tool.Also disclosed is a method for an integrated RCD current device and a computer program product.

Description

INTEGRATED RESIDUAL CURRENT DEVICE FOR HANDHELDWET TOOLS här -M-agiiæ:s--Rosén,vita-ifran-»känn-er-anal-.š-o-šfian--Berg TECHNICAL FIELDThe present invention relates generally to the field of residual current devices.More particularly, it relates to integrated residual current devices for electrical tools comprising a liquid system.

BACKGROUND For so called liquid system tools, i.e. electrical handheld, portable ortransportable power tools that operate with an internal or external liquid system, thereare national regulations dictating that the tool should typically be equipped with aresidual current device, RCD, or a ground fault circuit interrupter, GFCD (the termsmay be used interchangeably in this disclosure) for protection against hazardous groundfault current, in order to be allowed to be sold and marketed.

The liquid system typically functions as a cooler or cleaner for the electricaltool, however if a fault occurs there is a risk that liquid may escape the system and thathazardous currents may be lead by the liquid to the housing of the tool and possiblyharrn an operator of the tool.

The RCD prevents this from happening by measuring the electric currentﬂowing in the line conductors, or conductor wires, and comparing it to the electriccurrent ﬂowing in the retum conductor. If the sum of these currents is not zero, then it isan indication that the current is disappearing somewhere else, typically through theprotective earthed housing of the tool and possibly through the operator. When it isdetected that the sum of the currents is not zero or not above a threshold value, the RCD is configured to break the power so that no current flows in the tool. The RCD will trig again until the error resulting in the leaking currents and the ground fault has been takencare of.

A typical conventional RCD is installed at the extension cord or power cable ofthe electrical tool or at the main power entry, and is typically not able to detect errorsthat occur due to smooth DCs deviating within the tool. In order to also detect that aleaking smooth DC and high frequency (HF) currents are present, an additional RCDfor this purpose may be added to the regular RCD for detecting leaking DCs.

However, the typical implementation is expensive, bulky, fragile and not verysuitable for handheld of portable tools in construction environments.

Therefore, there is a need for an improved RCD for ground fault protection for liquid system tools.

SUMMARY It is an object of the teachings herein to provide a residual current device orground fault current interrupter which enables detection of leaking altemating currentsas well as leaking direct currents and high frequency currents.

According to a first aspect, this is achieved by an integrated residual currentdevice, RCD, for a liquid system tool. The liquid system tool comprises a current circuithaving a power input for receiving an altemating electrical current, AC, a rectif1er forrectifying the AC into a direct current, DC, a voltage booster for increasing a DCvoltage and a motor unit connected to an output of the voltage booster for driving theliquid system tool.

The integrated RCD comprises a sensor element connected to an output of therectifier and an input of the voltage booster and being configured to collect an analogcurrent signal. The integrated RCD also comprises an analog to digital, A/D, converterconfigured to convert the analog current signal into a digital current signal and a lo gicunit connected to the A/D converter.

The logic unit is configured to evaluate the digital current signal and compareit to a current requirement, wherein if the lo gic unit deterrnines that the digital currentsignal does not fulfill the current requirement, it is further configured to break the current circuit so that no current can flow in the liquid system tool.

In some embodiments, the liquid system tool comprises an electrical motor,and the motor unit is a motor inverter configured to provide the motor With a highfrequency current.

Thus the integrated RCD according to some embodiments may be integratedinto the liquid system tool and utilize some of the components Which are conventionallypresent Within the tool.

In some embodiments, the logic unit may be connected to the circuit breakerarranged at the power input, Wherein the lo gic unit is configured to break the currentcircuit by tripping the circuit breaker if the digital current signal does not fulf1ll thecurrent requirement.

The breaker may e. g. be a solenoid contactor relay.

In some embodiments, the motor unit may be a motor inverter generating ahigh frequency current.

In some embodiments, the sensor may comprise a pair of shunt resistorsconnected to the output of the rectifier, Wherein the A/D-converter is configured tomeasure the analog current signal over the shunt resistor pair and convert the analogcurrent signal into the digital current signal.

In some embodiments, the logic unit may be configured to receive ameasurement signal from at least one other component of integrated RCD and/or theliquid system tool and compare the measurement signal to the digital current signal.

In some embodiments, the at least one other component may be at least one ofa Voltage observer sensor and a current observer sensor.

In some embodiments, the at least one other component may be at least one ofthe voltage booster or the motor unit.

In some embodiments, the logic unit may be configured to determine based onthe comparison of the digital current signal and the measurement signal if the sensor isoperating correctly, and to break the current circuit if an error is detected.

In some embodiments, the logic unit may be configured to automaticallycompare the digital current signal to the measurement signal on a recurring basis.

In some embodiments, the comparison may be performed every time the liquid system tool is powered on.

In some embodiments, the electrical circuit may be driven by one phase sourceor two phase source or three phase source.

A second aspect is a liquid system tool comprising the integrated RCDaccording to the first aspect.

In some embodiments, the liquid system tool according to the second aspect isa handheld, portable, transportable or stationary electrical power tool.

A third aspect is a method for detecting residual current in a liquid systempower tool. The liquid system tool comprises a current circuit having a power input forreceiving an altemating electrical current, AC, a rectif1er for rectifying the AC into adirect current, DC, a voltage booster for increasing a DC voltage and a motor unitconnected to an output of the voltage booster for driving the liquid system tool motor.

The method comprises collecting an analog current signal from a sensorconnected to an output of the rectif1er and an input of the voltage booster andtransmitting the collected analog current signal to a logic unit connected to an analog todigital converter.

The method also comprises converting the analog current signal into a digitalcurrent signal, evaluating the digital current signal and comparing the digital currentsignal to a current requirement.

The method also comprises deterrnining if the digital current signal fulf1ll thecurrent requirement, and if it is deterrnined that the digital signal current does not fulf1llthe current requirement, the method comprises breaking the current circuit so that nocurrent can flow in the liquid system tool.

A fourth aspect is a computer program product comprising a computer readablemedium having stored thereon a computer program comprising program instructions,wherein the computer program is loadable into a data-processing unit, wherein thecomputer program is stored in a memory associated to the data-processing unit, andwherein the computer program is conf1gured to, when loaded into and run by the data-processing unit, cause the data-processing unit to execute method steps according to the third aspect.

In some embodiments, the first and/or second aspect may carry out the methodaccording to the third aspect.

In some embodiments, the second and third aspect may additionally share orhave identical features as those described in conjunction with the first aspect.

An advantage with some of the embodiments is that a cost effective and robustRCD is enabled capable of detecting various types of currents in a liquid system tool.

Another advantage with some of the embodiments is that only one RCD isneeded to detect AC-currents, DC-currents and HF-currents in a liquid system tool.

Another advantage of some of the embodiments is that the RCD is integratedinto the liquid system tool, resulting in that it may utilize already present conventionalcomponents in its implementation leading to cost efficiency.

Another advantage of some embodiments is that the integrated RCD is enabledto perform a self diagnosis and may continuously perform a self test of its components and functions leading to a safer device.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the teachings herein will be described in further detail in thefollowing with reference to the accompanying drawings which illustrate non-limitingexamples on how the embodiments can be reduced into practice and in which: Fig. l shows a schematic drawing of a liquid system tool comprising anexample integrated RCD according to some embodiments, Fig. 2 shows a schematic drawing of a liquid system tool comprising anexample integrated RCD according to some embodiments, Fig. 3 shows a schematic drawing of an example integrated RCD according tosome embodiments, Figs. 4A and 4B each show a schematic drawing of a liquid system toolcomprising an example integrated RCD according to some embodiments, Fig. 5 shows an example method for an integrated RCD according to someembodiments, and Fig. 6 shows a schematic drawing of an example computer program product according to some embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS The disclosed embodiments Will now be described more fully hereinafter Withreference to the accompanying drawings, in Which certain embodiments of the inventionare shown.

Fig. 1 shoWs a schematic drawing of an arrangement 100 of a liquid systemtool comprising an integrated RCD 102 according to some embodiments.

The integrated RCD 102 may be integrated into a liquid system tool and utilizesome of the tools conventional components. The liquid system tool may e.g. be anappliance or a machine classif1ed as handheld, portable or transportable equipment. E. g.the liquid system tool may be a handheld chainsaW, diamond drill, jack hammer,electrical saw, surface grinder and the like.

The liquid system tool may comprise a current circuit having a poWer input(Plug) 101 for receiving an altemating electrical current, AC, a rectif1er (Rec) 104 forrectifying the AC into a direct current, DC, a Voltage booster (Booster) 106 forincreasing a DC voltage and a motor unit (Drive) 111 connected to an output of thevoltage booster 106 for driving the liquid system tool.

The motor unit 111 may be a motor inverter of an electrical motor comprised inthe liquid system tool, configured to provide the electrical motor With a high frequency(HF) current.

The integrated RCD 102 may ﬁarther comprise a sensor element (Sen) 105connected to an output of the rectif1er 104 (Which may be a component that isconventionally present in the liquid system tool and not necessarily a part of theintegrated RCD 102 as indicated by the dashed box) and an input of the voltage booster106 and being configured to collect an analog current signal.

The integrated RCD 102 may also comprise an analog to digital converter(ADC) 109 conf1gured to convert the analog current signal into a digital current signaland a lo gic unit (Logic) 108 connected to the analog to digital converter 109.

The integrated RCD 102 may ﬁirther comprise a solenoid contactor relay (Con)103 configured to break the input current from the plug 101 if malﬁanction is detected.

In some embodiments, the arrangement 100 may further comprise a diagnosisunit (Diag) 107 configured to evaluate the performance of the logic unit 108. Thearrangement 100 may further comprise a stop switch (STOP) 110 configured to causethe solenoid contactor relay (Con) 103 to trip and break the input current from the plug1 0 1 .

The output of the stop switch 110 may be evaluated by the lo gic unit 108which trips the solenoid contactor relay 103 if leaking touch currents are detected.

The logic unit 108 may further be configured to evaluate the digital currentsignal and compare it to a current requirement, wherein if the logic unit deterrnines thatthe digital current signal does not fulf1ll the current requirement, it is further conf1guredto break the current circuit so that no current can ﬂow in the liquid system tool. Forinstance, the logic unit may in some embodiments cause the stop switch to trigger thesolenoid contactor relay 103 to trip and thus break the circuit such that the input currentfrom the plug 101 is stopped and the liquid system tool looses power.

If the digital current signal does not fulf1ll the current requirement, then that isan indication that the currents ﬂowing in the conductive wires of the liquid system toolare not equal to the current in the retum conductor, which in tum is an indication that amalfunction has occurred and currents are leaking away.

The current requirement may e.g. in some embodiments be that the currentﬂowing in the conductor wires should be equal to the current ﬂowing in the retum wireof the integrated RCD. Thus the current digital signal may represent the differencebetween the conductor currents and the retum current. In such case, the currentrequirement may be that that the digital current signal is zero or a low value, and anyother, or higher value will trigger the RCD to break the circuit.

In some embodiments, the digital current signal may represent a leakingcurrent and the current requirement may be a current threshold, which the digital currentsignal may not exceed, such as 6 mA, 10 mA or 30 mA, or that the frequency of theleaking currents may be between 0 Hz (DC) to 100 kHz (HF). A person skilled in the artwould easily realize that other values are possible, both higher and lower, and fall within the scope of the invention.

In order to break the current Circuit, the logic unit 108 may output a signal tothe stop switch 110, triggering it to stop the liquid system tool by causing the solenoidcontactor relay 103 to trip and break the circuit.

In some embodiments, the solenoid contactor relay 103 may e. g. be a breakeror a mains contactor relay arranged at the power input, Wherein the logic unit 108 isconf1gured to break the current circuit by tripping the breaker if the digital current signaldoes not fulf1ll the current requirement.

Furtherrnore, as elaborated on above, the integrated RCD according to someembodiments is integrated Within the liquid system tool. Thus, the RCD circuit 102comprising the contactor 103, rectif1er 104, sensor element 105, logic unit 108, analogto digital converter 109 may in some embodiments form an integrated current device(ICD). The ICD may thus constitute the actual implementation of the integrated RCDfor protection against hazardous ground fault current.

Thus, the term integrated RCD may be used interchangeably With the termintegrated current device (ICD) in this disclosure.

Furthermore, integrating the sensor element 105 between the rectifier 104 andthe voltage booster 106 makes it possible for the integrated RCD to detect and react toboth leaking altemating currents and direct currents, Without having to add an extraRCD just for detecting leaking smooth DC or HF currents.

This is possible since no matter What type of current gave rise to the error, itWill be reﬂected after the rectifier 104 Where the sensor element 105 can detect it. Thus,the sensor element 105 does not have to be aware of Whether it is a leaking ACs, DCsor HF currents.

In some embodiments, the logic unit 108 may be configured to continuouslyevaluate the digital current signal and immediately break the current circuit if the digitalcurrent signal does not fulfill the current requirement.

In some embodiments, the sensor element 105 may e. g. a current transducercomprising a pair of shunt resistors connected to the output of the rectifier, Wherein theADC 109 is configured to measure the analog current signal over the shunt resistor pair and convert the analog current signal into the digital current signal.

Fig. 2 shows how an integrated RCD, e. g. the integrated RCD of Fig. 1 may beintegrated into a liquid system tool according to some embodiments.

Fig. 2 illustrates a schematic view of different domains of a liquid system tool,such as the liquid system tool described in conjunction with Fig. 1. In short, the liquidsystem tool comprises some sort of input utilization power (e.g. one or two or threephase altemating current, plug 101 of Fig. 1) for powering the tool, an AC domain, anICD functionality, a DC domain, a high frequency (HF) domain and a tool component(TOOL).

The ICD functionality, DC domain, HF domain and part of the tool componentmay all operate mainly within a logic domain, i.e. they operate digitally.

Fig. 2 further illustrates how an arrangement 200 of an integrated RCD (e.g.the integrated RCD described in conjunction with Fig. 1) comprised in a liquid systemtool corresponds to the above described domains.

The arrangement 200 comprises a plug 210 for providing electrical current, anintegrated RCD 202, a voltage booster 220 for increasing a DC voltage being outputfrom the integrated RCD 202 and a motor unit (Drive) 230 connected to an output of thevoltage booster 220 for driving the liquid system tool. The motor unit 230 may furtherbe connected to a handheld part (HAND) 240 of the liquid system tool such as ahousing.

In some embodiments, the motor unit 230 may be comprised in an electricalmotor configured to drive the liquid system tool. The motor unit 230 may be a motorinverter conﬁgured to provide the electrical motor of the liquid system tool with a highfrequency current.

The integrated RCD 202 may comprise a solenoid contactor relay (Con) 203, arectifier (Rec) 204, a sensor element (Sen) 205, a logic unit (Logic) 208 and an analogto digital converter (ADC) 209.

The logic unit 208 may e.g. be, the logic unit 108 of Fig. 1, and may operate within the lo gic domain of the liquid system tool. It may thus be easilyintegrated into the liquid system tool and share the logic system of conventionally present components.

Furthermore, in some embodiments the logic unit 208 may receive data fromseveral different components in order to determine if an electrical malfunction hasoccurred and in such case trigger the breaker.

Since the sensor element 205 of the integrated RCD 202 may in someembodiments utilize the already present lo gic domain within the liquid system tool,another advantage of some of the embodiments can be achieved in that the integratedRCD may collect data from other sensors and functions present within the liquid systemtool. Hence, the integrated RCD may perform a self diagnosis or a self test of itsfunction in order to determine if it operates correctly by means of the integrated RCD.

Fig. 3 illustrates a schematic block diagram of an integrated RCD 300 (e. g. theintegrated RCD described in conjunction with any of Figs. 1-2), for a liquid system tool,receiving sensor inputs from several different sources. The block diagram of Fig. 3 maye. g. be a more detailed block view of an integrated RCD according to someembodiments.

The liquid system tool may comprise a current circuit having a power input forreceiving an altemating electrical current, AC, a rectifier (not shown) for rectifying theAC into a direct current, DC, a voltage booster (not shown) for increasing a DC voltageand a motor unit (not shown) connected to an output of the voltage booster for drivingthe liquid system tool.

The integrated RCD 300 may further comprise a circuit breaker 301 (e. g. thesolenoid contactor relay 103/203 or breaker of Figs. 1-2), a sensor element 302 (e. g. thesensor elements of any of Figs. 1-2), an analog to digital converter (ADC) 303 (e. g. theADC described in conjunction with any of the Figs. 1-2), a processor 304 (e.g. the logicunit and/or processor described in Figs. 1-2), a controller 305, other sensors 306 andother functions 307.

Furthermore, the sensor element 302 may be connected to an output of therectifier and an input of the voltage booster and be configured to collect an analogcurrent signal. The ADC 303 may be configured to convert the analog current signalinto a digital current signal. The processor 304 may be connected to the ADC 303,wherein the processor 304 is configured to evaluate the digital current signal and compare it to a current requirement. If the processor 304 deterrnines that the digital ll current signal does not fulfill the current requirement it is further configured to breakthe current circuit so that no current can ﬂow in the liquid system tool, by causing thebreaker 301 to trip, e.g. by open a switch, and break the circuit.

The current requirement may in some embodiments be that the current ﬂowingin a conductor wire should be equal to the current ﬂowing in a return wire of the liquidsystem tool. Thus the digital current signal may represent the difference between theconductor current and the return current. In such case, the current requirement may bethat the digital current signal is zero, and any other Value will trigger the integratedRCD 300 such that it breaks the circuit.

In some embodiments, the current requirement may be a current threshold,which the digital current signal may not exceed, such as 6 mA, 10 mA or 30 mA, or thatthe frequency of the leaking currents may be between 0 Hz to 100 kHz. A person skilledin the art would easily realize that other Values are possible, both higher and lower, andfall within the scope of the invention.

The controller 305 and processor 304 may in some embodiments be integratedinto one logic unit (e.g. the logic unit 108 of Fig. 1).

In some embodiments, the other sensors 306 and other functions 307 are not apart of the integrated RCD 300, but may instead originate from other componentsconventionally present in the liquid system tool.

For instance, the logic unit 305, 306 may be configured to receive ameasurement signal from at least one other component and compare the measurementsignal to the digital current signal.

The measurement signal may e.g. be output from the other sensors 306 or theother functions 307 which may be conVentionally present within the liquid system toolor within the integrated RCD 300.

For instance, in some embodiments, the liquid system tool may comprisedigital logic enabling a programming of the e.g. the electrical motor to hold a certainspeed and frequency. The high frequency current of the motor which may be induced by the motor unit may thus be based on a programmable parameter. 12 The same programmable parameter may be utilized by the processor 304 of theintegrated RCD 300. Thus the integrated RCD 300 may be seen as a cognitive sensor ordevice being able to react to both fixed and Variable parameters.

In some embodiments, the integrated RCD 300 may further comprise filters(not shown) for filtering the currents of the liquid system tool. The processor 304 mayutilize a fixed programmable frequency parameter of the motor, and may tune the filterssuch that they are tuned in on maximum sensitivity, e.g. 20 kHz.

The programmable frequency parameter may furtherrnore be variable and maychange over time, the processor 304 may in such case tune e.g. the filters for altematingcurrents such that they follow the frequency of the motor, typically in the range of l0-l000 Hz, and filters out all other unwanted altemating current frequencies. This leads tothat the integrated RCD 300 keeps its sensitivity to currents having a frequency of 50Hz.

In some embodiments, the at least one other component comprised in the liquidsystem tool is at least one of the voltage booster, or the motor unit. I.e. the voltagebooster may comprise sensors measuring the size of incoming and outgoing voltages,these values may be utilized by the logic unit or processor of the integrated RCD 300.

Altematively or additionally, in some embodiments, the integrated RCD 300may further comprise a voltage observer sensor and a current observer sensor formeasuring voltages and currents within the integrated RCD 300. The logic unit orprocessor 304 may further be configured to determine, based on the comparison of thedigital current signal and the measurement signal, if the sensor 302 or other componentsin the integrated RCD 300 are operating correctly, and to break the current circuit if anerror is detected.

If the integrated RCD 300 or the sensor 302 are operating correctly thereshould exist a correlation between its output values and the output values of the othersensors and functions. If the logic unit detects that the correlations are starting to differwithout there actually being present any leaking currents, it may draw the conclusion that some sensor is malfunctioning and can react by breaking the current. 13 In some embodiments, the integrated RCD 300 may further be connected to auser display which may show an error code or simple error LED lamp indicating to anoperator if sensor or other component malfunction is detected.

In some embodiments, the logic unit is configured to automatically comparethe digital current signal to the measurement signal on a recurring basis, i.e.automatically perform the self test or self diagnosis without it having to be initiated byan operator of the liquid system tool. This has an advantage in that operation of theliquid system tool is safe and reliable since it does not rely on the human factor to testits function.

Thus, the integrated RCD 300 may continuously and automatically diagnose orself test itself in order to ensure proper function and maximum security.

The comparison or self diagnosis may e.g. be performed every time the currentcircuit or liquid system tool is powered on, i.e. every time the liquid system tool is to beused.

Additionally or altematively, in some embodiments, the comparison or selfdiagnosis may be performed at recurring time intervals when the liquid system tool is inoperation, e.g. every hour, once a day, every half hour, etc. In some embodiments, theself diagnosis may be performed every time the liquid system tool is powered down.

Thus, a tool having an integrated RCD 300 according to the above will bereliable and safe for a user since it continuously evaluates its own performance andfunction.

Fig. 4A and 4B each illustrate a more detailed circuit of an exampleimplementation of an integrated RCD 400a, 400b for a liquid system tool according tosome embodiments.

The liquid system tool may e.g. comprise a current circuit having a power input(Ll, L2, L3) for receiving an altemating electrical current, AC, a rectif1er (RECT) 402for rectifying the AC into a direct current, DC, a voltage booster (not shown) forincreasing a DC voltage and a motor unit (not shown) connected to an output of thevoltage booster for driving the liquid system tool.

The power input may e.g. be the plug l0l, 220 of any ofthe Figs. l-2. Therectif1er 402 may e.g. the rectif1er l04, 203 of any of the Figs. l-2. 14 The integrated RCD 400a may further comprise a breaker 401 (e.g. the breaker103 203, 301 of any of the Figs. 1-3) configured to break an electrical Circuit, a currenttransducer 403 configured to convert the current to a voltage, analog to digitalconverters (ADC) 403a, 403b and being connected to a pair of resistors of the currenttransducer 403, digital isolators (ISO) 404, a processor (PROC) 405, a power supply406 to active parts (such as the processor 405), a user input device 407 and a statusdisplay 409.

The integrated RCD 400a may further be connected to a controller (CNTR)409 which is in connection with e.g. a housing (TOOL) 410 of the liquid system tool.The controller 409 may be part of a DC domain in the logic domain of the liquid systemtool, whereas the liquid system tool 410 may be in the HF domain in the logic domain(compare with Fig. 2).

The two resistors of current transducer 403 may be connected to a positive andnegative DC-pole outputted from the rectifier. Thus the current transducer 403 mayfunction as a sensor (e.g. the sensor element 105, 205, 302 of any of the Figs. 1-3)which compares the current running through each DC-pole (conductor current andretum current) by collecting an analog current signal from the DC-poles. In order toproperly evaluate the analog current signal, it may be transmitted to the ADC 403 a,403b where it is converted into a digital current signal.

The processor 405 is configured to evaluate the digital current signal andcompare it to a current requirement, wherein if the processor 405 deterrnines that thedigital current signal does not fulfill the current requirement it is further configured tobreak the current circuit so that no current can ﬂow in the liquid system tool.

The processor 405 may e.g. be the logic unit 108, 208 or the processor 304 ofany ofthe Figs. 1-3.

In some embodiments, the current transducer may collect two analog currentsignals, one for each resistor, and transmit them to the ADC 403 a, 403b for conversioninto two digital current signals. Then the logic unit may subtract one digital signal fromthe other and compare the remainder digital current signal to the current requirement. In such case, the current requirement may be that the remainder should be zero or below a low threshold value, and any other higher Value will trigger the integrated RCD to breakthe circuit.

In some embodiments, the current requirement may be a current threshold,which the digital current signal may not exceed, such as 6 mA.

In some embodiments, it is preferable that the current transducer 403 isarranged directly after the rectifier 402. Here it functions as a sensor element (e. g. thesensor element 105, 205, 302 of any of the Figs. 1-3), as elaborated on above, capableof monitoring the difference between a positive current output and a negative currentoutput from the rectifier 402 at the two DC-poles. The current transducer shouldpreferably be arranged where the altemating current is converted into a direct current inorder to be able to detect errors resulting from both type of currents, i.e. leakingaltemating currents and leaking direct currents. As a result, no extra RCD needs to beimplemented for detecting DC-errors or HF-errors, which is necessary in conventionalimplementations.

Furthermore, the user input 407 may e.g. be a power button or lever which anoperator or user of the liquid system tool may use in order to switch the tool on and offThe status display 408 may e.g. be a display which powers on when the liquid systemtool is being used and displays data such as when the liquid system tool last performed aself diagnosis, or if any malfunction has been detected.

The digital isolators 404 may ensure that proper isolation is achieved betweenthe analog and digital domain. The digital isolators may be any type of suitableconventional digital isolator. Thus, the voltage potential between the two poles Ip and Inof the sensors and ADCs 403,403a, 403b is isolated. This is also true for the highvoltage potential that may exist between ADCs and the processor 405. The voltagepotential between parts can vary from several hundred volts up to lkV.

Fig. 4B illustrates another detailed implementation of an integrated RCDaccording to some embodiments.

The integrated RCD 400b of Fig. 4B may, in some embodiments, share or havesimilar features as those described above for the integrated RCD 400a of Fig. 4A.

The liquid system tool may e.g. comprise a current circuit having a power input (L1, L2, L3) for receiving an altemating electrical current, AC, a rectif1er (RECT) 402 16 for rectifying the AC into a direct current, DC, a voltage booster (not shown) forincreasing a DC voltage and a motor unit connected to an output of the voltage boosterfor driving the liquid system tool.

The power input may e.g. be the plug l0l, 220 of any ofthe Figs. l-2. Therectif1er 402 may e.g. the rectif1er l04, 203 of any of the Figs. l-2.

The integrated RCD 400b may further comprise a breaker 40l conf1gured tobreak an electrical circuit, a current transducer 403 configured to convert the current toa voltage, analog to digital converters (ADC) 403 a, 403b connected to a pair of resistorsof the current transducer, digital isolators (ISO) 404, a processor (PROC) 405, a powersupply 406 to active parts (such as the processor 405), a user input device 407 and astatus display 408. The integrated RCD may further comprise a voltage observer 403c,403d, a current observer 403e, a controller 4l2 for a break load resistor, and the breakload resistor 4l l.

The integrated RCD 400a may further be connected to a controller (CNTR)409 which is in connection with e.g. a housing (TOOL) 4l0 of the liquid system tool.The controller 409 may be part of a DC domain in the logic domain of the liquid systemtool, whereas the liquid system tool 4l0 may be in the HF domain in the lo gic domain(compare with Fig. 2).

The two resistors of current transducer 403 may be connected to a positive andnegative DC-pole outputted from the rectif1er 402. Thus the current transducer 403 mayfunction as a sensor which compares the current running through each DC-pole(conductor current and retum current) by collecting an analog current signal from theDC-poles. In order to properly evaluate the analog current signal, it may be transmittedto the ADC 403a, 403b where it is converted into a digital current signal.

The processor 405 may e.g. be the logic unit l08, 208 and/or the processor 304of any ofthe Figs. l-3. 17 In some embodiments, the current transducer may collect two analog currentsignals, one for each resistor, and transmit them to the ADC 403 a, 403b for conversioninto two digital current signals. Then the processor 405 may subtract one digital signalfrom the other and compare the remainder digital current signal to the currentrequirement. In such case, the current requirement may be that the remainder should bezero or a very low threshold value, and any other higher value may trigger the integratedRCD to break the circuit.

In some embodiments, it is preferable that the current transducer 403 isarranged directly after the rectifier 402. Here it functions as a sensor element (e.g. thesensor element 105, 201, 302 of any of the Figs. 1-3) capable of monitoring thedifference between a positive current output and a negative current output from therectifier 402 at the two DC-poles, as elaborated on above.

The current transducer should preferably be arranged where the altematingcurrent is converted into a direct current in order to be able to detect errors resultingfrom both type of currents, i.e. leaking altemating currents and leaking direct currents aswell as high frequency currents from the motor of the liquid system tool. As, a result noextra RCD needs to be implemented for detecting DC-errors, which is necessary inconventional implementations.

The digital isolators 404 ensure that proper isolation is achieved between theanalog and digital domain.

The voltage observer 403c, 403d and the current observer 403e may enable theintegrated RCD 400b to measure voltage and current levels of its components in orderto regularly perform a self test or self diagnosis of the system as they function asadditional sensors. For instance, the voltage and current being observed or measured bythe respective observer should have a correlation if the components of the integratedRCD are functioning properly. If a non-correlation is detected between the observedvoltage and the observed current, then it is an indication that one or more of the components of the integrated RCD is not functioning properly and should be replaced. 18 Upon such detection, the integrated RCD may be configured to trigger, whichresults in a break of the power to the liquid system tool e. g. by causing the processor405 to break the circuit by means of the breaker 40l. The processor 405 may then beconfigured to cause the status display 409 to display an error message indicating to auser that something is malfunctioning in the integrated RCD.

In some embodiments, the voltage observer 403c, 403d and the currentobserver 403c may be implemented by means of one or more analog-to-digitalconverters.

In some embodiments, the integrated RCD 400b may receive additional sensoror functional inputs from other components comprised within the liquid system tool(compare with Fig. 3).

For instance, the processor 405 may be configured to receive a measurementsignal from at least one other component comprised in the liquid system tool andcompare the measurement signal to the digital current signal.

In some embodiments, the at least one other component comprised in the liquidsystem tool may e.g. be at least one of the voltage booster, or the motor unit. I.e. thevoltage booster may comprise sensors measuring the size of incoming and outgoingvoltages, these values may be utilized by the logic unit of the integrated RCD.

The logic unit may e.g. be configured to determine based on the comparison ofthe digital current signal and the measurement signal if the sensors is operatingcorrectly, and to break the current circuit if an error is detected.

In some embodiments, the electrical circuit described in any of the Figs. l-4may further be driven by one phase drive, two phase drive or three phase drive.

In some embodiments, the liquid system tool described in any of the Figs. l-4may be a portable or stationary electrical power tool.

Fig. 5 illustrates an example method 50l of an integrated residual currentdevice, RCD, for a liquid system tool. The liquid system tool may comprise a currentcircuit having a power input for receiving an altemating electrical current, AC, arectifier for rectifying the AC into a direct current, DC, a voltage booster for increasinga DC voltage and a motor unit connected to an output of the voltage booster for driving the liquid system tool. 19 The components and technical features of the integrated RCD and the liquidsystem tool may in some embodiments be the corresponding components as describedin conjunction with any of the Figs. 1-4.

The power input may e.g. be the plug 101, 220, and or L1-L3 of Figs 1, 2 and4, and the rectif1er may be the rectif1er 104, 203, and 402 of Figs 1, 2 and 4, etc.

The method 500 comprises collecting 501 an analog current signal from asensor (e.g. the sensor element of any of the Figs. 1-4) connected to an output of therectif1er and an input of the Voltage booster from the analog current, and transmitting502 the collected analog current signal to a logic unit connected to an analog to digitalconverter (ADC).

The logic unit may e.g. be the logic unit 105 and/or processor 204, 304, 405 ofany ofthe Figs. 1-4.

The method 500 also comprises converting 503 the analog current signal into adigital current signal. In some embodiments, the logic unit may be configured toperform this conversion.

When the digital current signal has been obtained, it is evaluated 504by thelogic unit and compared to a current requirement.

The logic unit may further determine 505 if the digital current signal fulf1lls acurrent requirement. The current requirement may e.g. be deterrnined as described inconjunction with any of the previous Figs. 1-4.

If it is deterrnined that the digital current signal does not fulfill the currentrequirement (No-path out of 505) then the lo gic unit causes a breaker to trip and break506 the current circuit so that no current can flow in the liquid system tool.

The logic unit may e.g. output a signal which triggers a main contactor relay totrip and thus break the power.

If it is deterrnined that the digital current signal fulf1lls the current requirement(Yes-path out of 505) the logic unit eValuates the digital signal again on a repeatedbasis.

Thus, the logic unit continuously evaluates the digital current signal and canimmediately break the current circuit if the digital current signal does not fulf1ll the current requirement.

In some embodiments, the sensor may collect two analog current signals, andtransmit them to the ADC for Conversion into two digital current signals. Then the logicunit may subtract one digital signal from the other and compare the remainder digitalcurrent signal to the current requirement. In such case, the current requirement may bethat the remainder should be zero, and any other value Will trigger the integrated RCDto break the circuit.

In some embodiments, the current requirement may be a current threshold,Which the digital current signal may not exceed, such as 2 mA, or a frequency thresholdof the current such as 40, 50 or 60 Hz. Thus the subtraction of the currents should notresult in a value exceeding the current threshold.

In some embodiments, the method 500 may further comprise receiving ameasurement signal from at least one other component of the liquid system tool andcomparing the measurement signal to the digital current signal.

The at least one other component may be comprised in the liquid system tooland may e.g. be at least one of the Voltage booster, or the motor unit.

In some embodiments, the measurement signal may altematively oradditionally be output from a Voltage observer and/or a current observer integrated intothe integrated RCD.

The method 500 may further comprise deterrnining based on the comparison ofthe digital current signal and the measurement signal if the sensor is operating correctly,and breaking the current circuit if an error is detected.

Thus the method enables the integrated RCD to perform a self test or selfdiagnosis of its functionality by collecting reference data Which, if it deviates from aknown value, indicates if a component in the integrated RCD is not functioningproperly (compare With Figs. 3 and 4).

The method 500 may further comprise automatically comparing the digitalcurrent signal to the measurement signal on a recurring basis.

The comparison may for instance be performed every time the current circuit(i.e. the liquid system tool) is powered on. Or, it may be performed at predeterrninedtime intervals, such as once every day, every Week, after l5 minutes of operation of the liquid system tool, etc. The result of the self diagnosis may then be displayed on a status 21 display, such that a user may know When the self test Was performed and if everythingis operating correctly.

In some embodiments, the sensor may comprise a pair of shunt resistorsconnected to the output of the rectifier. The method 500 may further comprisemeasuring the analog current signal over the shunt resistor pair and converting theanalog current signal into the digital current signal.

Fig. 6 illustrates a computer program product 600 according to someembodiments. The computer program product 600 may comprise a computer readablemedium having stored thereon a computer program comprising program instructions.The computer program may be loadable into a data-processing unit 601 comprising amemory (MEM) 602 and a processor (PROC) 603. The computer program may bestored in the memory 602 associated to the data-processing unit, and Wherein thecomputer program is configured to, When loaded into and run by the data-processingunit, cause the processor 603 to execute method steps according to the method 500.

Disclosed herein is a novel and inventive integrated RCD Which is capable ofdetecting errors resulting from leakage of both altemating and direct currents Within aliquid system tool.

Thanks to utilization of already present components and logic domain of theliquid system tool for implementing the integrated RCD, a cost effective and simpleimplementation is achieved.

Furthermore, the integrated RCD according to some embodiments disclosedherein is capable of perforrning an automatic self diagnosis or self test of itscomponents Which allows for errors to be quickly detected and components to bereplaced before they may cause any hazardous leaking currents. Thus, the integratedRCD according to some embodiments disclosed herein is proactive and makes it safer for a user to operate a liquid system tool.

Claims

1. A liquid system tool comprising a current Circuit having a power input (101,210) for receiving an altemating electrical current, AC, a rectif1er (104, 204, 402) forrectifying the AC into a direct current, DC, a voltage booster (106, 220) for increasing aDC voltage and a motor unit (111, 230) connected to an output of the voltage booster(106, 220) for driving the liquid system tool, characterized in that the liquid systemtool has an integrated residual current device, RCD, for protecting an operator of theliquid system tool against hazardous ground fault currents, the RCD comprising: a sensor element (105, 205, 302, 403a-e) connected to an output of the rectifier(104, 204, 402) and an input of the voltage booster (106, 220) and being configured tocollect an analog current signal, an analog to digital, A/D, converter (109, 209, 303, 403a, 403b) configured toconvert the analog current signal into a digital current signal; and a logic unit (108, 208, 304, 405) connected to the A/D converter (109, 209,303, 403a, 403b), wherein the logic unit (108, 208, 304, 405) is configured to evaluatethe digital current signal and compare it to a current requirement comprising a currentthreshold and/or a frequency range, and wherein if the logic unit deterrnines that thedigital current signal does not fulfill the current requirement, it is further configured to break the current circuit so that no current can ﬂow in the liquid system tool.

2. The liquid system tool according to claim 1, wherein the logic unit isconnected to a circuit breaker (103, 203, 301, 401) arranged at the power input (101,210), and wherein the logic unit (108, 208, 304, 405) is configured to break the currentcircuit by tripping the breaker (103, 203, 301, 401) if the digital current signal does not fulfill the current requirement.

3. The liquid system tool according to any of the previous claims, wherein thesensor element (105, 205, 302, 403a-e) comprises a pair of shunt resistors (403)connected to the output of the rectifier (104, 204, 402), and wherein the A/D-converter (109, 209, 303, 403a, 403b) is configured to measure the analog current signal over the 23 shunt resistor pair (403) and convert the analog current signal into the digital current signal.

4. The liquid system tool according to any of the previous claims, Wherein thelogic unit (108, 208, 304, 405) is configured to receive a measurement signal from atleast one other component of the integrated RCD and/or of the liquid system tool and compare the measurement signal to the digital current signal.

5. The liquid system tool according to claim 4, Wherein the at least one othercomponent is at least one of a Voltage observer sensor (403 e) and a current observer sensor (403c, 403d).

6. The liquid system tool according to claim 4, Wherein the at least one other component is at least one of the voltage booster (106, 220) or the motor unit (111, 230).

7. The liquid system tool according to any of claims 4-6, Wherein the logic unit(108, 208, 304, 405) is configured to determine based on the comparison of the digitalcurrent signal and the measurement signal if the sensor element (105, 205, 302, 403a-e) is operating correctly, and to break the current circuit if an error is detected.

8. The liquid system tool according to any of the claims 4 to 7, Wherein thelogic unit 108, 208, 304, 405) is configured to automatically compare the digital current signal to the measurement signal on a recurring basis.

9. The liquid system tool according to claim 8, Wherein the comparison is performed every time the liquid system tool is powered on.

10. The liquid system tool according to any of the previous claims, Wherein the current circuit is driven by one phase source or two phase source or three phase source. 24

11. The liquid system tool according to any preceding claim, wherein the liquid system tool is a handheld, portable, transportable or stationary electrical power tool.

12. A method for detecting residual current in a liquid system tool, wherein theliquid system tool comprises a current circuit having a power input for receiving analtemating electrical current, AC, a rectif1er for rectifying the AC into a direct current,DC, a voltage booster for increasing a DC voltage and a motor unit connected to anoutput of the voltage booster for driving the liquid system tool, the method comprising: collecting (501) an analog current signal from a sensor connected to an outputof the rectifier and an input of the voltage booster; transmitting (5 02) the collected analog current signal to a logic unit connectedto an analog to digital converter; converting (503) the analog current signal into a digital current signal; evaluating (5 04) the digital current signal; comparing (505) the digital current signal to a current requirement comprisinga current threshold or a frequency range, deterrnining if the digital current signal fulfill the current requirement; and if itis deterrnined that the digital signal current does not fulfill the current requirement: breaking (506) the current circuit so that no current can ﬂow in the liquid system tool.

13. The method according to claim 12, wherein the logic unit is connected to amains contactor relay arranged at the power input, and wherein the method furthercomprises breaking (5 06) the current circuit by tripping the mains contactor relay if it is deterrnined that the digital current signal does not fulfill the current requirement.

14. The method according to any of the claims 12-13, wherein the sensorcomprises a pair of shunt resistors connected to the output of the rectifier, and whereinthe method further comprises measuring the analog current signal over the shunt resistor pair; and converting the analog current signal into the digital current signal.

15. The method according to any of the claims 12-14, further comprisingreceiving a measurement signal from at least one other component of theintegrated RCD and/or of the liquid system tool; and comparing (5 04) the measurement signal to the digital current signal.

16. The method according to claim 15, Wherein the at least one other component is at least one of a voltage observer sensor and a current observer sensor.

17. The method according to claim 15, Wherein the at least one other component is at least one of the voltage booster or the motor unit.

18. The method according to any of the claims 15-17, further comprisingdeterrnining (505) based on the comparison of the digital current signal and themeasurement signal if the sensor is operating correctly, and breaking (506) the current circuit if an error is detected.

19. The method according to any of the claims 15-18, further comprisingautomatically comparing (504) the digital current signal to the measurement signal on a recurring basis.

20. The method according to claim 19, further comprising performing the comparison every time the current circuit is powered on.

21. The method according to any of the claims 12-20, further comprising driving the e .f m' cwirrfsrit circuit by one phase source, two phase source or three phase source.

22. A computer program product comprising a computer readable medium having stored thereon a computer program comprising program instructions, Wherein 26 the computer program is loadable into a data-processing unit, Wherein the computerprogram is stored in a memory associated to the data-processing unit, and Wherein thecomputer program is conﬁgured to, When loaded into and run by the data-processingunit, cause the data-processing unit to execute method steps according to any of the claims 12-21.